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United States Patent |
6,068,366
|
Bolash
,   et al.
|
May 30, 2000
|
Method of printing with an ink jet printer to inhibit the formation of a
print artifact
Abstract
The invention is directed to a method of printing on a print medium wherein
a relocation error is induced in a paper transport system so as to
randomize, bias, or redistribute harmonic errors associated with the paper
transport system. The print medium is advanced in the ink jet printer in
an advance direction to a registration location using the paper transport
system. A first subset of an addressable set of ink emitting orifices in
the printhead are used to print on the print medium at the registration
location. The print medium is then moved in a reverse direction a
predetermined distance. The print medium is again advanced in the advance
direction and relocated at the registration location using the paper
transport system. A second subset of the addressable set of ink emitting
orifices in the printhead are used to print on the relocated print medium
at the registration location.
Inventors:
|
Bolash; John Philip (Lexington, KY);
James, III; Edmund Holin (Lexington, KY)
|
Assignee:
|
Lexmark International, Inc. (Lexington, KY)
|
Appl. No.:
|
309369 |
Filed:
|
May 11, 1999 |
Current U.S. Class: |
347/43; 347/16 |
Intern'l Class: |
B41J 002/21; B41J 029/38 |
Field of Search: |
347/43,40,16,104,105
346/134
400/279
|
References Cited
U.S. Patent Documents
5684517 | Nov., 1997 | Clemente et al. | 347/43.
|
5751312 | May., 1998 | Gibson | 347/43.
|
5940093 | Aug., 1999 | Bolash et al. | 347/16.
|
Primary Examiner: Le; N.
Assistant Examiner: Nguyen; Thinh
Attorney, Agent or Firm: Sanderson; Michael T.
Parent Case Text
This is a continuation of application Ser. No. 08/818,055 filed Mar. 14,
1997 issued as U.S. Pat. No. 5,940,093 filed Aug. 17, 1999.
Claims
What is claimed is:
1. A method of printing on a print medium using a printhead in an ink jet
printer, said method comprising the steps of:
printing on the print medium at a first location using a first addressable
set of ink emitting orifices in said printhead;
in the presence of a harmonic error in said print medium transport system,
moving the print medium in a reverse direction using a print medium
transport system a predetermined distance associated with said harmonic
error in said print medium transport system;
advancing the print medium in an advance direction using said print medium
transport system; and
printing on the relocated print medium at a second location using a second
addressable set of ink emitting orifices in said printhead, said second
addressable set of ink emitting orifices being different than said first
addressable set of ink emitting orifices.
2. The method of printing of claim 1, wherein said predetermined distance
comprises a distance which is sufficient to induce a relocation error in
said print medium transport system.
3. The method of printing of claim 2, wherein said relocation error is
associated with at least one gear in said print medium transport system.
4. The method of claim 1, further comprising the step advancing the print
medium prior to performing said moving step.
5. The method of claim 1, wherein said second location corresponds to the
first location plus or minus a distance associated with a relocation error
induced by said print medium transport system.
6. The method of claim 1, wherein said first location is a first
registration location and said second location is a second registration
location.
7. The method of printing of claim 6, wherein said first registration
location is different from said second registration location.
8. The method of printing of claim 1, wherein said first and second
printing steps comprise the substeps of scanning the printhead across the
print medium in a direction transverse to said advance direction.
9. The method of printing of claim 1, wherein said moving step occurs after
a second advancing of the print medium using said print medium transport
system.
10. The method of printing of claim 1, wherein said first addressable set
of ink emitting orifices is the same as said second set of ink emitting
orifices.
11. The method according to claim 1, wherein said harmonic error occurs
with a frequency substantially equal to a rotational frequency of at least
one gear in said print medium transport system.
12. The method according to claim 11, comprising the further step of
cyclically repeating said moving step with a frequency dependent upon said
rotational frequency of said at least one gear in said print medium
transport system.
13. A method of printing on a print medium using a printhead in an ink jet
printer, said method comprising the steps of:
advancing the print medium in said ink jet printer in an advance direction
to a first registration location using a print medium transport system,
said first registration location including a harmonic error caused by said
print medium transport system;
printing on the print medium at said first registration location using a
first addressable set of ink emitting orifices in said printhead;
moving the print medium in a direction parallel to said advance direction a
distance which is sufficient to cause a relocation error in said print
medium transport system, said relocation error at least partially
offsetting said harmonic error caused by said print medium transport
system;
locating the print medium at a second registration location using said
print medium transport system; and
printing on the located print medium at said second registration location
using a second addressable set of ink emitting orifices in said printhead,
said second addressable set of ink emitting orifices being different than
said first addressable set of ink emitting orifices.
14. The method of printing of claim 13, wherein said moving step comprises
moving the print medium in a reverse direction a predetermined distance.
15. The method of printing of claim 13, wherein said first and second
printing steps comprise the substeps of scanning the printhead across the
print medium in a direction transverse to said advance direction.
16. The method of printing of claim 13, wherein said first registration
location is different from said second registration location.
17. The method of printing of claim 13, wherein said moving step occurs
after said locating step.
18. The method of printing of claim 13, wherein said first addressable set
of ink emitting orifices is the same as said second set of ink emitting
orifices.
19. The method of claim 13, wherein said distance is a variable distance.
20. The method of printing of claim 13, wherein said relocation error is
induced to randomize or redistribute harmonic error in said print medium
transport system.
21. The method of printing of claim 20, wherein said relocation error is
associated with at least one gear in said print medium transport system.
22. A method of printing on a print medium using a printhead in an ink jet
printer, said method comprising the steps of:
advancing the print medium in said ink jet printer in an advance direction
to a first registration location using a print medium transport system;
printing on the print medium at said first registration location;
advancing the print medium again in said advance direction and locating the
print medium at a second registration location using said print medium
transport system;
moving the print medium in a first direction parallel to said advance
direction;
moving the print medium in a second direction opposite to said first
direction to thereby locate the print medium at a randomized second
registration location; and
printing on the relocated print medium at said randomized second
registration location.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ink jet printers, and, more particularly,
to a method of printing using an ink jet printer to inhibit the formation
of a print artifact.
2. Description of the Related Art
Color ink-jet printers commonly use a tri-color cyan, magenta and yellow
ink cartridge, and a separate single color black ink cartridge. Each
cartridge contains multiple orifices through which the distribution of ink
onto a page can be controlled. Since the majority of printed documents
contain primarily black text, the number of black orifices is normally
several times larger than the number of orifices for each of the cyan,
magenta, or yellow inks. For example, the tri-color cartridge may contain
16 orifices each for cyan, magenta, and yellow, and the black cartridge
may contain 48 black orifices. For manufacturing reasons, there typically
exists a four-orifice tall gap between the cyan and magenta orifices, and
another four-orifice tall gap between the magenta and yellow orifices.
To render a full color image, the tri-color and black cartridges are passed
across a print medium such as paper in a horizontal direction
perpendicular to the vertical direction of alignment of the orifices in
the cartridges. Between passes of the cartridges, the print medium is
moved in the advance direction. For a raster, or row of printed dots,
which contains at least one of each of cyan, magenta, yellow, and black
dots, the color cartridge must be passed at least three times, once
passing to deposit any cyan dots present in the given raster, once passing
to deposit any magenta dots, and once passing to deposit any yellow dots.
Additionally, the black cartridge must be passed at least once. Of course,
for any pass of the color head all 48 color orifices can be used,
depositing the cyan, magenta, and yellow inks at different raster
locations. The most time efficient technique for depositing ink therefore
causes the tri-color cartridge to pass across each raster of the page at
most three times, and the black cartridge at most one time.
With a conventional method of printing with a tri-color ink jet printer as
described above, objectionable print artifacts may occur because of the
sequencing and/or timing between the placement of the different color ink
dots on the print medium. For example, print artifacts such as horizontal
color/black banding or intercolor bleeding may occur.
One known solution to the problem of a color/black banding artifact is
known as shingling or interlaced printing. For a 50% shingling mode (i.e.,
2-pass or 50% interlace level), approximately 50% of the dots are placed
on any given pass of the cartridge. The candidate dots are selected
according to a checkerboard pattern. The remaining 50% of the dots are
placed on a subsequent pass of the cartridge. For a raster which contains
cyan, magenta, yellow, and black dots, the color cartridge must be passed
at least six times, twice depositing any cyan dots present in the given
raster, twice depositing any magenta dots, and twice depositing any yellow
dots. Additionally, the black cartridge must be passed at least twice.
Another type of print artifact which may occur during printing and is not
associated with the sequencing and/or timing between placement of the
different color ink dots on the print medium is related to the paper
transport system which transports the paper through the ink jet printer in
the advance direction. The paper transport system must accurately align
the paper in the advance direction at a plurality of locations allowing
the cartridges to be scanned across the paper at a plurality of
corresponding rasters. The paper transport system typically includes a
plurality of rollers which are driven by a plurality of corresponding
gears. The gears include a limited degree of manufacturing tolerances
allowing sufficient clearances and preventing binding therebetween during
use. These manufacturing tolerances may cause errors in the exact
placement of each raster relative to a registration location of the paper.
Moreover, the stepper motor used to drive the gears includes certain
inherent errors associated with movement of the motor between steps. These
errors are referred to as "step-to-step errors" and are specified by the
manufacturer. Since the stepper motor and gears are rotated, these errors
tend to repeat on a cyclical basis, dependent upon the particular
rotational orientation of the gears as the gears rotate. The errors
associated with the paper transport system therefore tend to be harmonic
in nature, dependent upon the particular rotational orientation of the
gears. Thus, a print artifact having a "rainbow effect" in color samples
and gray scale darkness shifts in monochrome samples may occur in the
print image on the paper.
What is needed in the art is a method of printing which inhibits the
formation of print artifacts associated with harmonic errors in the paper
transport system of the ink jet printer.
SUMMARY OF THE INVENTION
The present invention provides a method of printing with an ink jet
printer, wherein a relocation error is induced in the registration
location of the print medium between printing scans so as to inhibit the
formation of a print artifact.
The invention comprises, in one form thereof, a method of printing on a
print medium, such as paper, using a printhead in an ink jet printer. A
first subset of an addressable set of ink emitting orifices in the
printhead are used to print on the print medium at a first location. The
print medium is then moved in a reverse direction a predetermined
distance. The print medium is again advanced in the advance direction and
relocated at a second location using the print medium transport system. A
second subset of the addressable set of ink emitting orifices in said
printhead are used to print on the relocated print medium at the
registration location.
An advantage of the present invention is that print artifacts caused by
harmonic errors in the print medium transport system are inhibited.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and advantages of this invention,
and the manner of attaining them, will become more apparent and the
invention will be better understood by reference to the following
description of an embodiment of the invention taken in conjunction with
the accompanying drawings, wherein:
FIG. 1 is a diagrammatic view of a tri-color cartridge having cyan, magenta
and yellow orifices and a black cartridge having black orifices, which may
be used with the method of the present invention; and
FIG. 2 illustrates an embodiment of a method of printing of the present
invention for reducing print artifacts associated with harmonic errors of
the paper transport system, using the printhead of FIG. 1 during
interlaced printing with 50% shingling (2-pass) for color and black.
FIG. 3 is a flowchart illustrating one embodiment of the method of the
present invention;
FIG. 4 is a flowchart illustrating another embodiment of the method of the
present invention; and
FIG. 5 is a flowchart illustrating yet another embodiment of the method of
the present invention.
Corresponding reference characters indicate corresponding parts throughout
the several views. The exemplification set out herein illustrates one
preferred embodiment of the invention, in one form, and such
exemplification is not to be construed as limiting the scope of the
invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, an example of a conventional print cartridge which
may be used with the method of the present invention is described in
greater detail. A color cartridge 10 and black cartridge 12 are carried by
a movable carriage (not shown). Color cartridge 10 includes a tri-color
printhead defined by a plurality of orifices 14, 16 and 18 for depositing
three respective colors of ink on a print medium, such as paper. Orifices
14 define a first array of orifices having a height H.sub.1, from which a
yellow ink may be jetted onto the print medium. Orifices 16 define a
second array of orifices having a height H.sub.2, from which a magenta ink
may be jetted onto the print medium. Orifices 18 define a third array of
orifices having a height H.sub.3, from which a cyan ink may be jetted onto
the print medium. Color cartridge 10 is therefore capable of jetting three
primary color inks onto the print medium using yellow orifices 14, magenta
orifices 16 and cyan orifices 18.
In the particular embodiment shown, yellow orifices 14, magenta orifices 16
and cyan orifices 18 each include sixteen (16) orifices, with each array
of orifices being disposed in two vertical rows of eight (8) orifices. A
distance "A" exists between vertically adjacent orifices 14, 16, and 18.
Yellow orifices 14, magenta orifices 16 and cyan orifices 18 are
incorporated into a one-piece cartridge in the embodiment shown. It should
be appreciated, however, that color cartridge 10 may be constructed as a
multiple-piece cartridge, such as a three-piece color cartridge
corresponding to each of the color orifices 14, 16 and 18.
Black cartridge 12 includes a black printhead defined by a plurality of
orifices 20 defining an array of orifices having a height H.sub.4.
Orifices 20 are configured to jet a single color ink, namely black ink, on
the print medium.
Referring now to FIG. 2, an embodiment of the method of printing of the
present invention for reducing print artifacts associated with harmonic
errors of a paper transport system will be described. In the embodiment
shown in FIG. 2, the method of the present invention is carried out using
color cartridge 10 and black cartridge 12 shown in FIG. 1, during
interlaced printing with 50% shingling (2-pass) for color and black.
Paper 24 is moved through the ink jet printer using a paper transport
system defined in part by a roller 26. Roller 26 frictionally engages
paper 24. Roller 26 includes a gear 28 which is attached to or integral
with an end thereof. Gear 28 includes a plurality of teeth around the
circumference thereof which enmesh with teeth on adjacent gears (not
shown) in the paper transport system. Rotation of the rollers within the
paper transport system, such as roller 26, causes paper 24 to move in the
advance direction indicated in FIG. 2.
Roller 26 is also used to align paper 24 at a registration location
allowing color cartridge 10 and black cartridge 12 to be aligned relative
to and scanned across a plurality of rasters. In the embodiment shown in
FIG. 2, the registration location is arbitrarily selected as corresponding
to a leading edge 30 of paper 24. That is, the distance between leading
edge 30 of paper 24 and a particular raster may be determined for
accurately locating color cartridge 10 and black cartridge 12 relative to
the particular raster. However, the registration location can be selected
to correspond to any location in the advance direction on paper 24. To
wit, leading edge 30 of paper 24 may be detected with appropriate sensors
and the number of steps associated with a stepper motor used to drive
roller 26 may be determined to locate any arbitrarily chosen registration
location on paper 24.
A conventional 50% shingling method (with reference to FIG. 2, but
disregarding the method of the present invention) involves scanning the
color cartridge and placing 50% of the color dots (first pass), moving the
paper a distance of 8 orifices (8 * distance A in FIG. 1), scanning the
color cartridge and placing 50% of the color dots (second pass), moving
the paper a distance of 8 orifices, scanning the color cartridge and
placing 50% of the color dots (third pass), moving the paper a distance of
8 orifices, scanning the black cartridge placing 50% of the black dots
(fourth pass), not moving the paper, and repeating this sequence (fifth
pass, etc.) until the entire document has been printed. A 50% shingling
technique as shown in FIG. 2 has the advantage of reducing the
objectionable color/black banding artifact previously described. Since
only part of the dots are placed on a given pass, some of the dots are
given time to dry into the paper prior to additional dots being placed.
Other levels of shingling are also possible, for example 25% shingling
(4-pass shingling) where approximately 25% of the dots are placed on any
given scan of the cartridges.
According to the method of the present invention, paper 24 is moved from an
initial registration location in a reverse direction between scans of
color cartridge 10 and black cartridge 12 a distance which is sufficient
to induce a relocation error as a result of a relocation of paper 24
nominally at the initial registration location, but actually to a second
registration location. Thus, the second registration location corresponds
to the initial registration location plus or minus the distance associated
with the relocation error. This relocation error may be induced in either
a random or synchronous manner with respect to the harmonic error
associated with the paper transport system. The reverse direction of
movement of paper 24 is parallel to but opposite from the advance
direction. Between each of the first through the fifth scans shown in FIG.
2, paper 24 is moved in the reverse direction a predetermined distance "D"
which is sufficient to cause a relocation error in the drive train of the
paper transport system, such as a displacement error associated with the
rotational movement of gear 28 of roller 26. The predetermined distance
"D" represents the distance which paper 24 is moved in the reverse
direction to cause an error in the paper transport system. In the
particular embodiment described herein, the predetermined distance "D" is
actually more than the distance "A" (FIG. 1) between vertically adjacent
pixels. However, in some embodiments, the distance "D" may be equal to or
less than "A". Thus, for example, a preferred range of the distance "D"
may be between 1/3 to six times the distance "A". In the particular
embodiment of FIG. 1, the distance "D" is preferably between about two to
three times the distance "A". The distance "D" can nonetheless be any
predetermined distance which effects a relocation error to randomize, or
bias, the harmonic disturbances in the paper transport system. For
example, the harmonic error may be randomized by varying the distance "D"
from one inducement of relocation error to the next, or the harmonic error
may be biased, or redistributed, by selecting a fixed value for the
distance "D". The predetermined distance "D" is shown exaggerated in FIG.
2 for purposes of illustration and clarity.
When carrying out a 50% shingling method as shown in FIG. 2 in conjunction
with the method of the present invention, color cartridge 10 is aligned
with a first registration location and scanned across paper 24 to
selectively deposit ink onto paper 24 from yellow orifices "Y", magenta
orifices "M" and cyan orifices "C" (shown in flow chart form in blocks 40
and 42 in FIG. 3). Upon completion of the first scan, paper 24 is advanced
a distance corresponding to eight vertically adjacent orifices and aligned
with a second registration location (block 44). When the registration
location corresponds to leading edge 30 of paper 24, yellow orifices "Y"
will thus be disposed a further distance away from leading edge 30 at the
second registration location. When positioned at the second registration
location, paper 24 is then moved in the reverse direction a predetermined
distance "D" causing a relocation error in the paper transport system
(block 46), and thereafter moved in the advance direction back to the
second registration location (block 48). Color cartridge 10 is then
scanned across paper 24 (block 50). Because the second registration
location is not aligned relative to the first registration location as a
result of the induced relocation error, print artifacts such as rainbow
effects in color samples and gray scale darkness shifts in monochrome
samples are avoided. The printing process of scanning color cartridge 10
or black cartridge 12, advancing paper 24 to a next registration location,
moving paper 24 in a reverse direction to induce a relocation error in the
paper transport system, relocating paper 24 at the next registration
location with the induced relocation error and printing on paper 24 at the
next registration location is repeated until the entire print image is
printed on paper 24.
In the embodiment of the method of the present invention described above,
the predetermined distance "D" is more than the distance "A" between
vertically adjacent orifices in color cartridge 10 or black cartridge 12
and preferably is about two to three times the distance "A". However, the
predetermined distance "D" may vary depending upon the manufacturing
tolerances of the various components in the paper transport system. The
predetermined distance "D" may be relatively easily determined using
empirical testing to establish what predetermined distance "D" is required
to avoid the formation of print artifacts associated with harmonic errors
in the paper transport system.
Additionally, in the embodiment described above, paper 24 is moved in the
reverse direction an amount which is sufficient to induce a relocation
error in the paper transport system. It is also to be understood, however,
that paper 24 may be moved in the advance direction as long as a
relocation error is likewise induced in the paper transport system prior
to locating or relocating paper 24 at a particular registration location.
Moreover, in the embodiment shown in FIG. 2 and described above, paper 24
is moved in the reverse direction after color cartridge 10 and black
cartridge 12 are located relative to a particular scan of the printhead,
and before the scan actually occurs. However, it is also possible to scan
the printhead, move paper 24 in the reverse direction an amount sufficient
to induce a relocation error in the paper transport system, advance paper
24 in the advance direction to the next registration location and then
scan the printhead for the next scan. That is, the relocation error may be
induced into the paper transport system prior to moving the paper to the
next registration location, rather than after the paper is located at the
next registration location (FIG. 4).
Additionally, the method of the present invention is described above with
reference to and in conjunction with a shingling algorithm. However, the
method of printing of the present invention may also be carried out using
a conventional printing technique without shingling. That is, paper 24 may
be advanced in the advance direction between scans of color cartridge 10 a
distance corresponding to the height of yellow orifices "Y", magenta
orifices "M" or cyan orifices "C". A relocation error associated with the
paper transport system is induced into the registration location for each
scan of color cartridge 10 and/or black cartridge 12. The relocation error
may be induced into the registration location either immediately before or
immediately after the paper is located at the particular registration
location, or may also be induced immediately after a particular scan and
before the paper is moved to the next registration location.
Furthermore, when the method of the present invention is utilized in
conjunction with a non-shingled printing technique, the first registration
location and the second registration location occurring before and after
movement of the paper to induce a relocation error may in fact coincide or
be the same registration location. To wit, a color cartridge 10 as shown
in FIG. 1 may be scanned across paper 24 and only one-half of the ink dots
placed on paper 24 during the scan. Paper 24 may then be moved in a
reverse direction to induce a relocation error and relocated at the same
registration location. Color cartridge 10 may then be scanned a second
time across paper 24 to deposit the remaining ink dots on paper 24 (FIG.
5). It will be appreciated, however, that an induced relocation error is
associated with each separate scan of color cartridge 10.
It is to be understood, and it will be appreciated by those skilled in the
art, that the methodology and logic of the present invention described
above may be carried out using any number of structural configurations
such as electronic hardware, software, and/or firmware, or the like.
While this invention has been described as having a preferred design, the
present invention can be further modified within the spirit and scope of
this disclosure. This application is therefore intended to cover any
variations, uses, or adaptations of the invention using its general
principles. Further, this application is intended to cover such departures
from the present disclosure as come within known or customary practice in
the art to which this invention pertains and which fall within the limits
of the appended claims.
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